Near-infrared electrogenerated chemiluminescence of Au22(glutathione)18 nanoclusters in aqueous solution and its analytical application

Abstract Gold nanoclusters (AuNCs) have attracted great attention in analytical sciences because they have unique optical and electrochemical properties with low biological toxicity. However, the analytical application of Au NCs-based electrogenerated chemiluminescence (ECL) still remains relatively unexplored largely due to their low ECL efficiency in aqueous solution. Moreover, the precise information of molecular formula of Au NCs have not been determined in large number of reports. In the present study, the ECL behavior of atomically precise Au22(SG)18 NCs, where SG is glutathione, were characterized in the aqueous solution. The oxidation of Au22(SG)18 NCs together with coreactant tripropylamine (TPA) at the working electrode potential of 1.25 V vs Ag/AgCl (3 M NaCl) has led to strong ECL emission at ~767 nm in the near-infrared region. The ECL intensity of the Au22(SG)18 NCs was about 14-fold higher than the ECL intensity obtained with the Au@BSA NCs, which is most commonly used Au NCs in aqueous solution. The ECL intensity is strongly dependent upon the concentrations of Au22(SG)18 NCs and TPA. However, the ECL intensity of Au22(SG)18 NCs with TPA is diminished in the presence of phenolic compounds depending upon their concentrations. Using catechol as a model analyte, the present ECL system can detect it in the linear range from 1.0 × 10−7 to 1.0 × 10−4 M with a detection limit of 3.3 × 10−9 M (S/N = 3). The present study has demonstrated the potential application of the Au NCs-based ECL in real analytical problems.